Tension controlled thread feeding system

ABSTRACT

A system, apparatus and method for tension control in a thread feeding system that provides a fast and reliable method for feeding high tack elastomeric thread or fiber from a package to a thread processing system. A drive and tension control apparatus at least one of increments, maintains or decrements the speed of a driven take-off roll when the tension is out of a predetermined range of operation. A tension controller devices measures tension and determines whether the average tension for the moving threads is out-of-range relative to the predetermined tension values for the threads. Alarms and other indicators may also be used to determine the threads are at least one of broken, not moving and out-of-range for tension control.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent application Ser. No. 10/722,261, filed Nov. 25, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thread feeding system or fiber unwinding device, and more specifically to a system or device that minimizes average tension levels and tension variations of a plurality of elastomeric threads or fibers being transported to a downstream thread or fiber processing operation.

2. Description of Background Art

The most common method of unwinding thread or fiber from a cylindrical mandrel (or “package”) in manufacturing processes is referred to as “rolling takeoff”. It should be noted that the terms “thread” or “fiber” are used interchangeably throughout this document. When the package is exhausted the empty mandrel must be removed and a new package installed. This operation requires shutting down the manufacturing line causing unproductive downtime.

Another method often utilized, the over end takeoff (OETO) method, allows continuous operation, because the terminating end of the thread or fiber wound on an active package can be attached to the leading end of the thread or fiber wound on a standby package. This allows the active package to be fully exhausted at which point the standby package becomes the active package, all without any process interruption. However, unacceptable variations in threadline tension are common with OETO.

Research Disclosure, p. 729, November 1995, item #37922, discloses an OETO system in which elastomeric thread or fiber is passed through a system comprising a relaxation section and motor driven nip rolls, before being fed to the manufacturing line. The relaxation section, extending between the package and the nip rolls, is stated to suppress tension variations. However, threads or fibers that exhibit high cohesive forces (generally referred to as “tack”) display unusually high variations in frictional forces and tension levels as the package unwinds. The slackness of the thread line in the relaxation region can vary and can result in temporarily excessive amounts of filament being unwound from the package. This excess thread or fiber can be drawn into the nip rolls and wound up on itself leading to entanglement or breakage of the threadline requiring the manufacturing line to be stopped. The high level of tack contributes to the possibility of the excess fiber adhering to it and to the nip rolls. The OETO device can also be configured such that the thread or fiber horizontally traverses the relaxation section. In this case, the fiber then travels through nip rolls whose axes are vertical. However, in this configuration, the thread or fiber in the region between the package and the nip rolls can sag. This sagging allows the threadline position on the nip rolls to become unstable and can result in interference between adjacent threadlines.

U.S. Pat. Nos. 3,797,767; 3,999,715 and 6,158,689 disclose the use of spirally grooved rolls in thread or fiber winding machines in order to impart a specified pitch angle to a fiber as it is wound on a package. The use of grooved rolls for maintaining positional stability among a plurality of thread lines on a single roll is not described.

U.S. Pat. No. 5,566,574 (Tiziano) discloses a method for feeding a thread or fiber to a textile machine by utilizing a braking member and actuator to adjust the tension and feed rate of the thread or fiber. However, Tiziano does not disclose the concept of utilizing a variable speed electrical motor for a driven roll, where the speed of the motor is determined based on a range of desired thread tensions, is not disclosed. In addition, an elastomeric thread or fiber like Spandex, which has a unique inherent finish texture that differs from threads or fibers used in the textile industry, requires an electrical motor feeding device that allows the Spandex to remain in contact with the driven feed roll attached to the motor. Further, Spandex has a higher tensile strength specification and other characteristics that differ from fibers used in the textile industry. For example, threads or fibers typically used in the textile industry are specified in the range of 50-100 decitex(decigrams per kilometer) and tend to operate at lower rotation speeds of 1-50 feet/minute when being unwound from a package as compared to those used for elastomeric threads which typically are specified in the range of 600-1500 decitex and with higher rotation speeds of 300-400 feet/minute. Moreover, Tiziano is not directed to operate with or feed systems that require high tack, elastomeric threads such as Spandex.

The aforementioned problems make the processing of high tack, elastomeric threads or fibers particularly problematic. Fiber tack and its associated problems have been addressed by using topical fiber additives (prior to winding) or by unwinding the package and re-winding it on a new mandrel. However, both approaches add additional expense. Furthermore some applications (e.g., manufacturing of diapers and other personal care products) require the use of as-spun thread or fiber that is substantially finish-free and, consequently, exhibits high tack. Therefore, a fast and reliable method of unwinding and feeding high tack elastomeric thread or fiber from a package to a thread processing system is still needed in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates the fiber unwinding test equipment used to obtain the data in Examples 1-4.

FIG. 2 shows a perspective drawing of a preferred embodiment of an OETO unwinding device/thread feeding system.

FIG. 3 illustrates a perspective view of a portion of an unwinding device/thread feeding system of the invention including some of the packages, threadline guides and the first driven roll.

FIG. 4 is a top view of an unwinding device/thread feeding system of the invention.

FIGS. 5A and 5B are back and side views, respectively, of an unwinding device/thread feeding system of the invention.

FIG. 6 is a schematic top plan view of a diaper making thread processing system and the thread feeding system of the invention.

FIG. 7 is a front elevational view of the thread feeding system showing four feed roll packages, a support frame and a drive and tension control apparatus.

FIG. 8 is a top plan view of thread feeding system shown in FIG. 7.

FIG. 9 is an exemplary enlarged front elevational view of a four thread drive and tension control apparatus.

FIG. 10 is a top plan view of the four thread drive and tension control apparatus shown in FIG. 9.

FIG. 11 is a right side elevational view of the four thread drive and tension control apparatus shown in FIG. 9 and FIG. 10.

FIG. 12 is an exemplary perspective view showing a single thread drive and tension control apparatus.

FIG. 13 is a front elevational view showing two drive and tension control apparatus, each having four active feed roll packages.

FIG. 14 is an exemplary perspective view showing another drive and tension control apparatus.

FIG. 15 is a top plan view of the drive and tension control apparatus shown in FIG. 14.

FIG. 16 is another exemplary embodiment of thread feeding system with multiple drive and tension control apparatuses.

FIG. 17 is another exemplary perspective view showing a single thread drive and tension control apparatus.

FIG. 18 is an exemplary enlarged front elevational view of a second embodiment of a single thread drive and tension control apparatus.

FIG. 19 is a right side elevational view of the single thread drive and tension control apparatus shown in FIG. 18.

FIG. 20 is a top plan view of the single thread drive and tension control apparatus shown in FIG. 18.

FIG. 21 an exemplary enlarged front elevational view of a third embodiment of a single thread drive and tension control apparatus.

FIG. 22 is a top plan view of the third embodiment of the single thread drive and tension control apparatus shown in FIG. 21.

FIG. 23 shows a flow diagram of the method of monitoring thread tension of the present invention.

SUMMARY OF THE INVENTION

The present invention is a system, apparatus and method for tension control in a thread feeding system that provides a fast and reliable method for feeding high tack elastomeric thread or fiber from a package to a thread processing system.

In a first embodiment, the present invention provides a thread feeding system comprising: a support frame; a package holder affixed to said support frame for holding a package of thread about a rotational axis such that at least one thread can unwind from the package in a direction defining an acute angle (θ) with the rotational axis of the package; a driven take-off roll for unwinding thread from the package at a predetermined take-off rate: a first static guide for directing thread unwound from the package, said first static guide positioned on said frame such that; a distance (d) from the first static guide to the end of the package facing the first static guide, measured on the line defined by the rotational axis of the package, is equal to: at least about 0.41 meter for thread with tack of greater than about 2 grams OETO and less than about 7.5 grams OETO; or from about 0.71 meter to about 0.91 meter for fiber with tack greater than about 7.5; an angle (θ), defined by the intersection of imaginary lines corresponding, respectively, to the rotational axis of the package and the central axis of the first static guide inlet orifice that is equal to: 0° to about 30° for threads with tack greater than about 2 grams OETO and less than about 7.5 grams OETO; or 0° to about 10° for threads with tack levels greater than about 7.5 grams OETO; and a drive and tension control apparatus for sensing and controlling the speed of the driven take-off roll, wherein the drive and tension control apparatus controls the speed of a variable-speed motor for the driven take-off roll by determining whether at least one of the mean tension and maximum tension is within a predetermined range of thread tension values.

In another embodiment of the present invention is a drive and tension control apparatus comprising: guide rolls configured to guide at least one thread through a thread path of the drive and tension control apparatus; a driven take-off roll configured to move the at least one thread through the drive and tension control apparatus; a variable-speed motor configured to drive the driven take-off roll; a tension sensor configured to determine the tension on the at least one thread; a tension controller device configured to at least one of increment, maintain and decrement a speed of the variable-speed motor, wherein the guide rolls are located before and after the driven take-off roll, the tension sensor is located after the driven take-off roll, and wherein the speed of the variable-speed motor is maintained within a predetermined range of thread tension values by the tension controller device.

The above embodiments of the present invention preferably further include a second thread guide positioned between the package and the first thread guide for directing thread unwound from the package. More preferably, the present invention further comprises a third thread guide positioned between the first thread guide and the driven take-off roll. Further, this embodiment of the present of invention may also include a fourth thread guide positioned between the third thread guide and the driven take-up roll. Furthermore, at least one of the thread guides may be a grooved roll or the driven take-off roll may be a grooved roll.

Moreover, in a preferred embodiment, at least one thread guide is a static circular guide having a wear-resistant surface for contacting the thread. The static circular thread guide preferably has a wear-resistant inner surface such that the wear-resistant surface is the inner surface of an annulus.

In yet another embodiment, the present invention is a method for controlling thread tension in a thread feeding system, comprising: determining whether threads are broken; determining whether threads are moving; measuring the tension of the moving threads; determining whether any of the moving threads have a tension that is out-of-range relative to predetermined tension values; at least one of incrementing and decrementing the speed of a driven take-off roll when the tension is out of range and at least one of the number of increments and decrements is below a correction threshold;

-   -   determining whether an average tension for the moving threads is         out-of-range relative to the predetermined tension values for         the threads; at least one of incrementing and decrementing the         speed of a driven take-off roll when the tension is out of range         and at least one of the number of increments and decrements is         below a correction threshold; and setting an alarm when the         threads are at least one of broken, not moving and out-of-range         and above a correction threshold, wherein the value that         determines that the tension is out-of-range are in accordance         with predetermined tension values for the threads.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, a package 10 is maintained in a desired orientation by a cylindrical rod (not shown). The diameter of the rod is smaller than the diameter of the open core of the package such that the package can be slid over the suitably positioned rod and such that the thread or fiber can be unwound from the package by over end takeoff. The thread or fiber is then directed, in sequence, through a static guide 20 having a substantially circular orifice; a driven roll 30 around which the fiber is wrapped 360°, or less; and a second, driven take-up roll or set of rolls 50. The static guide is typically an orifice whose inner surface can be a highly polished ceramic material. Such a surface can provide excellent wear resistance and low friction. The take-up roll or rolls 50 representing that part of the manufacturing process equipment to which the thread or fiber is being supplied, is/are rotated at a speed relatively higher than the first motor-driven roll 30, so as to provide the desired draft. A distance (d) between the package and the static guide 20, which is at least about 0.43 meter and preferably not more than about 0.91 meter, can be maintained for operation with high tack fibers. An acute angle (θ), defined by the intersection of the imaginary lines corresponding, respectively, to the rotational axis of the package and the central axis of the static guide orifice that is perpendicular to the plane of the orifice, is preferably maintained between 0 and about 30° for operation with high tack fibers. Means for stabilizing the position of the threadline on the first driven roll can be provided by, for example, use of one or more additional guides 60, 70, 80 and/or a plurality of grooves in the surface of the first driven roll 30 wherein said grooves are substantially perpendicular to the roll 30 axis and substantially parallel to the direction of travel of the threadline.

Distances less than 0.41 meter can result in undesirably large tension variations. These variations can cause process control difficulties and can also lead to thread line breakages. Distances longer than 0.91 meter make the unwinding equipment less compact and ergonometrically less favorable. As the level of tack exhibited by the fiber increases, the minimum allowable distance, d, increases. For fibers with tack levels greater than about 2 and less than about 7.5, d is preferably at least about 0.41 meter; and for fibers with tack levels greater than about 7.5, d is preferably at least about 0.71 meter.

As the level of tack exhibited by the fiber increases, the maximum allowable angle, θ, decreases. The directional change of the threadline, as it passes through the first static guide, as measured in terms of θ, is preferably limited to between 0° and about 30° for fibers with tack levels greater than about 2 and less than about 7.5, and between 0° and about 10° for fibers with tack levels greater than about 7.5. Larger angles can result in excessive variations in thread line tension and draft, or even threadline breakage.

The desired thread line positional stability can be assured by providing grooves in the surface of the first driven roll 30. Such grooves also allow closer spacing of the threadlines, thereby minimizing the dimensions of the equipment. The resulting stability of the threadline position also allows operator intervention to correct a threadline problem, while the process is running, with less risk of disturbing adjacent thread lines.

Threadline guides can be used in addition to, or instead of, grooved rolls to impart thread line stability and to direct the threadline along a desired path. Of the various threadline guides available, captive, rolling guides are preferred. The use of a single, first motor-driven roll described above is found to give outstanding process performance without the need for employing the more mechanically complex and expensive nip rolls described in Research Disclosure, item 37922, cited above. A wrap of 360° or less of the thread line around the roll 30 minimizes fiber-on-fiber contact and the possibility of fiber damage associated with such contact. Less than 360° contact between the thread line and roll can be achieved by the appropriate positioning of a threadline guide placed immediately after the roll to lift the fiber off the roll surface short of a complete 360° wrap.

The process by which the unwinder of this invention can be operated involves the following steps, with reference to FIGS. 2, 3, 4, 5A and 5B: a) placing the fiber packages on their respective mounting rods; b) tying the leading end of fiber from each standby package 300′ or 400′ to the trailing fiber end of its corresponding active package 300 or 400, respectively; c) directing the leading fiber end of each active package through its respective static guide 100 or 100′, then through a wrap of 360° or less around the first driven roll 800 and then causing it to be engaged by a take-up device not shown in FIGS. 2-5 (identified as 50 in FIG. 1) (this device, typically a driven roll or set of driven rolls, represents that element of the manufacturing process which first engages the fiber as it exits the unwinder); d) initiating rotation of the first driven roll 800 and take-up device (not shown); while e) controlling the surface speeds of each such that the surface speed of roll(s) (not shown) exceeds that of roll 800 by the percentage corresponding to the desired fiber elongation (or draft); f) replacing each active package 300 or 400, as it becomes exhausted, with what now becomes a standby package 300′ or 400′; and g) tying the leading fiber end of this new standby package 300 or 400 with the trailing end of the now, active package 300′ or 400′. Repeating steps f and g (or b), as required, allows uninterrupted operation.

As previously described, positional stabilization of the threadlines can be achieved by the use of a grooved roll 800, and/or additional threadline guides. In the event that a grooved roll is employed, step c, above, also includes placing each fiber in its corresponding groove. In the event that additional threadline guides are employed, additional steps must be added to the above procedure to thread each fiber through its respective, additional guides in the sequence that such guides are encountered.

FIGS. 2-5A&B illustrate a preferred embodiment of an OETO unwinding device for high tack spandex fiber. For the purpose of improved clarity, the threadlines are not shown. As presented in FIGS. 2, 3 and 4, the OETO fiber unwinding system has the capacity to feed a manufacturing line with eight (8) threadlines, requiring a capacity to accommodate sixteen (16) packages. Each threadline supplied from an active package to the first static guide 100 or 100′ is kept in the horizontal plane. The packages are mounted in vertical tiers 200, each tier holding four (4) packages 300, 300′, 400 and 400′. The four packages are arranged in pairs, each pair consisting of one active 300 or 400 and one standby 300′ or 400′ package.

With reference to FIGS. 3, 4, 5A and 5B, each threadline leads from an active package 300 or 400 through a first static guide 100 or 100′ and then through a captive rolling guide 500, at the horizontal center of the unwinding device. All three of these elements are located substantially on the same horizontal plane.

In particular, referring to FIG. 3, the threadline is then turned up or down, depending upon the tier from which it originated, to the vertical center of the unwinding device. At the vertical center of the unwinding device, each threadlines is fed through its respective captive rolling guide 600 and then directed horizontally through its respective static guide 700. Finally, the threadlines are wrapped 360°, or less, around a horizontal driven roll 800. The driven roll 800 (shown in FIG. 3) is illustrated with eight grooves 900, through which the threadlines run. The groove depths are 0.38 mm and the spacing between the grooves is 15 mm. Grooves are an optional feature of horizontal driven roll 800; the driven roll may alternatively have a smooth surface.

The following examples include experiments with Lycra® XA® fibers having no topically applied finish.

EXAMPLE 1

The test equipment used in obtaining the data for this and the following examples, could be configured in various ways, such as optionally including or excluding certain design elements and changing the sequence of certain elements. The equipment configuration employed for this example, with reference to FIG. 1, was comprised of the following elements, listed in the order in which they were encountered by the moving threadline: fiber package 10, static guide 20, first, driven roll 30, tension sensor 40, and driven take-up rolls 50.

The test equipment geometry and other experimental test conditions are summarized below:

The distances between the static guide 20 and the first driven roll 30, between the first driven roll 30 and the tension sensor 40 and between the first driven roll 30 and the take-up roll 50 were 0.22, 1.94 and 2.1-3.4 meters, respectively. In this example, the first driven roll 30, having a diameter of 8.89 cm. was not grooved. The threadline was maintained in the horizontal plane (relative to ground), and its directional change within that horizontal plane as it passed through the static guide, was maintained constant at 0° θ. The distance between the package 10 and first guide 20 was varied. The threadline was wrapped 360° around the first driven roll 30. The threadline draft was controlled at 2.15×. by maintaining the surface speeds of the first roll 30 at 93.4 meter/min, and the surface speed of the take-up rolls 50 at 294.3 meters/min.

Tension data (expressed in grams) were collected with a Model PDM-8 data logger, and a Model TE-200-C-CE-DC sensor (Electromatic Equipment Co.). All tension measurements were averaged over five-minute run time using a data sampling frequency of approximately 82 samples/sec.

“Mean range tension” was determined as follows: within every 1.25-second interval of the tension measurement, the minimum and maximum tension levels were recorded (yielding 103 data points). Mean range tension was calculated by averaging the differences (between the minimum and maximum values) over the 5-min run.

The fiber evaluated in this test was as-spun Lycra® XA® spandex (a registered trademark of E.I. du Pont de Nemours and Company) having a linear density of 620 dtex (decigram per kilometer).

Table 1 shows the thread line tension variations, as measured at the sensor, as the distance, d, between the package and the static guide was varied over a distance between about 0.25 and 0.81 meter. TABLE 1 Distance Means Range Max. Tension (meter) Tension (grams) (grams) 0.27 16.90 50.00 0.28 17.60 50.00 0.30 17.80 50.00 0.33 16.30 50.00 0.36 1630 49.00 0.38 14.50 50.00 0.41 13.70 48.40 0.43 13.30 38.00 0.46 12.40 37.10 0.48 12.20 44.70 0.51 11.60 36.30 0.53 11.60 36.70 0.56 11.60 30.40 0.58 11.80 32.60 0.61 10.00 28.80 0.64 10.60 34.30 0.66 10.60 25.30 0.69 10.40 34.30 0.71 10.60 29.80 0.74 10.00 28.40 0.76 10.40 29.40 0.79 10.80 27.80 0.80 10.80 34.50

Table 1 demonstrates that thread line tension (expressed either as the mean range or the maximum tension) decreases as the distance between the package and the static guide is increased. Minimum tensions, not shown in the table ranged from about 0.6 to 1.4 grams. Unexpectedly, it has been discovered that there is a minimum distance of about 0.41 meter below which the absolute level of tension and the tension variability (as observed by plotting, for example, maximum tension versus distance) rises to an unacceptably high level identifiable by the occurrence of threadline breakages which are usually preceded by a relatively abrupt increase in mean range tension.

EXAMPLE 2

The same test equipment as described in Example 1, but configured to more closely correspond to the preferred embodiment of the OETO unwinder design was utilized. With reference to FIG. 1, the equipment had the following elements in the order in which they were encountered by the moving threadline: fiber package 10, captive rolling guide 60, static guide 20, captive rolling guide 70, first, driven roll 30, captive rolling guide 80, tension sensor 40, and driven take-up rolls 50.

The distances between the static guide 20 and the first driven roll 30, between the first driven roll 30 and the tension sensor 40, and between the first driven roll 30 and the take-up rolls 50 were 0.43, 0.51 and 2.43 meters, respectively. The first driven roll 30 was a single roll having a single groove with a depth of 0.38 mm. The threadline was again maintained in the horizontal plane. The distance between the package and the static guide 20 was held constant at 0.65 meter while the angle, θ, was varied. Threadline draft was maintained at 4× by controlling the first driven roll 30 and the take-up rolls 50, respectively, at surface speeds of 68.6 and 274.3 meters/min.

In addition to monitoring threadline tension as in Example 1, tension spikes were also recorded. “Tension spikes” are the average number of sudden increases in tension greater than 25 grams above baseline tension in a 5-min period.

Various as-spun Lycra® XA® spandex fibers, exhibiting different levels of tack, were evaluated. Tack levels were characterized by measuring the OETO tension (in grams) by the following method: The fiber package and a ceramic pig tail guide were mounted 0.61 meter apart, such that the axes of each were directly in line. The fiber is pulled off the package over end at a threadline speed of 50 meters/min, through the guide, and through a tension sensor.

Table 2 shows the threadline tension variations as the angle θ increased; where θ is defined as the acute angle made by the intersection of the imaginary lines corresponding, respectively, to the rotational axis of the package and the central axis of the static guide orifice that is perpendicular to the plane of the orifice. TABLE 2 Mean Max. Angle Range Tension Tension Fiber (decree) Tension (g) (grams) Spikes Tack T-127 0 38.4 174.9 56 620 dtex 5 40.8 176.5 85 Lot 9291 11 BROKE Merge 1Y331 22 BROKE 45 BROKE T-127 0 16.5 118.4 0 620 dtex 5 17.3 119.2 0 Lot 0211 11 17.3 122.4 0 Merge 16398 22 18.8 124.7 0 45 20.4 131.8 0 57 25/1 138.0 1 67 29.0 149.0 9 77 30.6 156.9 11 90 35.3 167.9 14 T-162B 22 32.9 171.8 16 11.368 800 dtex 45 40.8 198.4 53 ″ Lot 0205 57 44.7 >200 72 ″ Merge 16525 T-162C 22 25.9 159.2 0 7.02 800 dtex 45 29.8 176.5 4 ″ Lot 0020 57 31.4 169.4 24 ″ Merge 16600

Examination of the data in the above table reveals an unexpected relationship between threadline tension and the angle between the centerlines of the package 10 and the static guide 20. As the angle increases so does thread line tension, and tension spikes occur more frequently. At sufficiently large angles, thread line breakage can occur. The sensitivity of thread line tension to the angle traversed by the thread line as it passes through the guide is dependent upon the properties of the fiber. The data of Table 2 indicates that fibers characterized by higher tack exhibit higher sensitivity of thread line tension with respect to this angle. For some fibers that exhibit an exceptionally high level of tack, the angle above which thread line breakage cannot be avoided is less than about 10°.

EXAMPLE 3

This series of runs, using the test equipment described previously and configured as in Example 2, evaluated the effect of angle on threadline tension for fibers of different tack levels. The distance, d, between the package and the static guide 20 was maintained constant at 0.65 meter. Threadline draft was maintained at 4× by controlling the first driven roll 30 and the take-up rolls 50, respectively, at surface speeds of 68.6 and 274.3 meters/min. All other experimental conditions were as described for Example 2. The data are summarized in Table 3. TABLE 3 Mean Max. Angle Range Tension Tension Fiber (decree) Tension (g) (grams) Spikes Tack T-162C 0 25.1 164.7 2 7.02  800 dtex 5 25.1 157.7 0 ″ Merge 16600 11 27.5 156.9 0 ″ Lot 0020 22 28.2 160.0 0 ″ 45 36.9 182.8 16 ″ 57 42.4 196.1 59 ″ 67 47.8 >200.0 127 ″ 77 BROKE T-162C 0 18.8 150.6 0 1.408 As-spun 5 15.7 142.8 0 ″ 840 den 11 17.3 143.5 0 ″ Merge 16795 22 14.9 140.4 0 ″ Lot 1019 45 14.9 138.8 0 ″ 57 ″ 67 15.7 140.4 0 ″ 90 17.3 145.1 0 ″ T-162 B 0 29.0 171.8 13 11.368  800 dtex 5 32.2 172.6 10 ″ Merge 16525 11 36.1 184.3 42 ″ Lot 0205 22 39.2 >200.0 43 ″ 45 52.6 >200.0 126 ″ 57 BROKE ″

The high tack fibers tested in this series of runs are the same as two of the fibers tested in Example 2. Comparison of the data for these same fibers in Tables 2 and 3, shows that thread line tension increases with increasing angle, and thread line breakage may occur at excessively high angles. (In contrast, fibers containing finish can be run at angles of up to and including 90° with no increase in thread line tension, no occurrence of tension spikes and no thread line breaks. When Lycra® XA® T-162C fiber, 924 dtex den, merge 16795(lot 1019), finish, having a tack of 1.406, was run at angles of 0-90°, there was no threadline tension increase and no tension spikes.)

These data demonstrate that limiting the angle the thread line traverses as it passes through the first static guide provides uninterrupted manufacturing processing even for high tack fiber threadlines.

EXAMPLE 4

This series of runs using the test equipment described previously and configured as in Example 2, evaluated the effect of the distance, d, between the package and the static guide on threadline tension for fibers of different tack levels. The angle, θ, was maintained constant at 22°. The threadline draft was controlled at 4× and the take-up speed at 274.3 meters/min. TABLE 4 Mean Range Max. Tension Tack Fiber Distance (meter) Tension (g) (grams) (grams) T-162 C 0.20 56.5 >200 7.02 As-spun 0.30 44.7 200.0 ″ 720 den 0.41 32.2 182.0 ″ Merge 16600 0.51 32.2 174.9 ″ Lot 0020 0.61 31.4 181.2 ″ 0.71 29.0 173.3 ″ 0.81 29.8 178.8 ″ 0.91 32.2 173.3 ″ 1.02 29.0 167.9 ″ T-162 B 0.20 BROKE BROKE 11.368 As-spun 0.30 57.3 >200 ″ 720 den 0.41 56.5 >200 ″ Merge 16525 0.51 55.7 >200 ″ Lot 0205 0.61 56.5 200.0 ″ 0.71 56.5 200.0 ″ 0.81 48.6 200.0 ″ 0.91 50.2 200.0 ″ 1.02 52.6 200.0 ″

The test results for these fibers show the minimum distance between the package and the fixed guide below which the threadline tension and mean range tension increase unacceptably. The value of this minimum depends upon the tack level of the fiber being tested. In contrast, there is essentially no effect of package-to-static guide distance on the lower tack Lycra® spandex. These results reinforce the difficulty in maintaining smoothly running process conditions with high tack fibers. The present invention allows successful control of processes utilizing such fibers.

EXAMPLE 5

A test of the operation of the unwinder system of this invention, as pictured in FIGS. 2-5, was conducted under commercial production conditions using fibers that were characterized by different levels of tack. Table 5 summarizes these test results. Data were obtained as in previous examples, except that each of the tension measurements reported is the average of a minimum of 4 separate measurements, each measurement consisting of one tube running for a 10-min period. Similarly, each number of tension spikes, as reported in Table 5, is the average number of spikes greater than 25 grams above baseline tension in a 10-min period. Measurements were made on packages that were nearly full (surface) or nearly empty (core). Core measurements are those with about 1.6-cm thickness of thread or fiber remaining on the tube. Of the 5 as-spun fibers run, 4 ran with no operational problems. One fiber sample, Merge 1Y331, did result in an unacceptable occurrence of tension spikes. That fiber demonstrated an unusually high level of tack, even for as-spun fiber, as evidenced by the fact that the mean range tension was over 60% higher than that of the fiber exhibiting the next highest level of tack. TABLE 5 Mean Linear Fiber Range Max. Density Location Speed Fiber Tension Tension Tension Fiber (dtex) on Tube (ft/min) Draft (grams) (grams) Spikes Merge 16398 620 Surface 274.3 4X 12.3 10016 0 Merge 16398 620 Surface 121.9 4X 12.5 96.1 0 Merge 16398 620 Core 274.3 4X 17.5 110.7 0 Merge 16398 620 Core 121.9 4X 16.3 104.1 0 Merge 1Y331 620 Surface 274.3 4X 28.6 151.4 18

FIG. 6 is a exemplary schematic top plan view of a thread processing 101 and the thread feeding system 103 of the invention. According to an exemplary application, as thread exits the thread feeding system 103, the thread engages a take-up device (not shown) of the thread processing system 101. The take-up device is commonly a driven roll or a set of driven rolls that pull the thread from thread feeding system 103. The movement of the take-up device of the thread processing system 101, discussed in detail below, causes the thread to unwind from an active package 105. As the thread unwinds from an active package 105, the thread follows a predetermined thread path before reaching a drive and tension control apparatus 110. Preferably the thread path is configured, as discussed above, to minimize the addition of unintended tension to the elastomeric thread before reaching the drive and tension control apparatus 110 whenever practically possible.

FIG. 7 is a front elevational view of the thread feeding system 103 showing a support frame 109 with four feed roll packages 105, 106, 107, 108, a guide system 112A, 112B and a drive and tension control apparatus 110 mounted on the support frame 109. FIG. 8 is a top plan view of the thread feeding system 103 shown in FIG. 6 and FIG. 7. Thread feeding system 103 is preferably configured as a single unit, as shown. In alternative embodiments, thread feeding system 103 may not include each of support frame 109, guide system 112A, 112B drive and tension control apparatus 110 as a single unit, but instead may comprise any combination of separate units that define a thread feeding system. In all embodiments of the present invention, support frame 109, guide system 112A, 112B, drive and tension control apparatus 110 cooperate to provide the thread feeding system 103 with a method for monitoring and adjusting the net tension of a thread group or the tension of a single thread by at least one of increasing, maintaining or decreasing the thread tension of the thread group or thread; and providing uniformity and increased efficiency to the operation of the thread feeding system.

Referring to FIG. 7 and FIG. 8, support frame 109 is a structure functioning as a creel to support and position the thread that is fed to a thread processing system (FIG. 6, 101) by the thread feeding system 103. Elastomeric thread is generally placed on support frame 109 in the form of active packages 105, 106, 107, 108 and standby packages (FIG. 8, 105′, 106′ and 107′,108′ (not shown)). As used herein, the term “package” is used to describe elastomeric fabric that has been wound around an object. “Active package” refers to the package that is currently being unwound. “Standby package” refers to a package that is connected to the end of the active package and will be unwound when the thread on the active package is exhausted. Preferably, all packages are spools of elastomeric threads or fibers and have been wound around a hollow cylindrical object or core. The configuration of packages, as shown in FIG. 7 and FIG. 8, is not intended to be limiting and is illustrated for exemplary purposes only. As can be appreciated, the present invention is applicable with elastomeric fibers or threads provided in any configuration.

The support frame 109 shown in FIG. 7 and FIG. 8 is a frame-like structure designed to support active packages 105, 106, 107, 108 and standby packages (FIG. 8, 105′, 106′ and 107′, 108′ (not shown)). Support frame 109 preferably includes at least one end frame member 122, each having at least one projection 124 located on opposite ends of each of the frame members to support the active and standby packages. Preferably, the projections 124 are cylindrical rods having a cross-section smaller than the cross section of the opening of the hollow cylindrical object or core of the active packages 105, 106, 107, 108 and standby packages 105′, 106′ and 107′, 108′.

FIG. 7 illustrates that the thread path is defined by the positioning of the packages 105-108, 105′-108′ and the configuration of guide system 112A, 112B. According to a preferred embodiment, the distance between the packages 105-108, 105′-108′ and drive and tension control apparatus 110 should be minimized when practically possible. Parameters for optimum configurations of an unwinding device/thread feeding system in terms of both the distance and angle of the packages have been discussed above. A substantial distance between the packages 105-108, 105′-108′ and the drive and tension control apparatus 110 may undesirably add tension to the thread before reaching drive and tension control apparatus 110. However, in alternative embodiments, it may be preferable not to minimize the distance between the packages 105-108, 105′-108′ and the drive and tension control apparatus 110 in accordance with the parameters discussed above.

As shown in FIG. 8, packages 105, 105′, 106, 106′ are positioned on the projections 124 in such a manner that the thread can be unwound and supplied to the drive and tension control apparatus 110. According to a preferred embodiment, the thread feeding system 103 is an “over end take off” (OETO) thread feeding system. The OETO method involves tying the tail end of the thread of the active packages 105, 106 to the lead end of the thread of standby packages 105′, 106′, as shown in FIG. 8. The OETO method is intended to allow the active packages to become fully exhausted of thread and to then allow for a continuous transition to the standby package without requiring the thread feeding system to be shut down. As can be appreciated, the present invention is not limited to thread feeding systems utilizing the OETO method, and includes any other take off methods that are generally known or otherwise appropriate.

Thread feeding system 103, as shown in FIG. 7 and FIG. 8, may include more than one active package 105, 106, 107, 108 and is configured to supply multiple elastomeric fibers or threads 104 to a thread processing system (FIG. 6, 101) as a thread group. Preferably, thread feeding system 103 is configured to supply multiple thread groups for more than one application. For example, in a diaper manufacturing system, it is generally known to include an elastic band feature near the open end of each leg to help retain moisture in the diaper and for a snug fit around the legs. The elastic band feature for each leg may be provided by using one or more elastomeric fibers or threads.

As shown in FIG. 8, the multiple elastomeric fibers or threads 104 supplied to each leg constitute a thread group and hence two threads groups could be provided to a diaper manufacturing system (i.e., one thread group for each leg). For example, as shown in the FIG. 8, thread feeding system 103 is configured to supply two thread groups, each having two elastomeric threads per thread group to a thread processing system. In alternative embodiments, thread feeding system 103 may be configured to supply any number of thread groups each having any number of threads per thread group. Support frame 109 may be configured to meet such demands.

FIG. 9 is an exemplary enlarged front elevational view of a four thread drive and tension control apparatus 110 mounted on the support frame 109. The drive and tension control apparatus 110 comprising a driven take-off or driven take-off roll 111, guide rolls 113A-113A′″ to 113E-113E′″, a tension sensors 115′-115′″, motion sensors 116-116′″, breakage sensors 117-117′″ and a tension controller device 119. The tension controller device 119 further comprises a graphical display 121, a keyboard 123 for data entry and control, and alarm lights 125 to indicate alarm conditions to the operator. Static guides 128 and captive rolling guides 129 that are external to the drive and tension control apparatus 110 are also shown in FIG. 9.

As shown in FIG. 9, guide system 112A, 112B are used to direct the thread towards the drive and tension control apparatus 110. In particular, when the thread feeding system 103 is feeding multiple threads, the multiple guide systems 112A, 112B may be needed to direct the threads to drive and tension control apparatus 110 so that the threads do not tangle. Preferably the thread path for each thread is isolated relative to the other threads, other than the time that the threads are in contact with the driven take-off roll 111 as will be discussed below.

In addition, it has been contemplated that the use of guide systems 112A, 112B, as most clearly shown in FIG. 10, may be required for safety reasons. Further guide systems (not shown) may be used to direct the thread to the take-up device of the thread processing system (FIG. 6, 101) after passing through drive and tension control apparatus 110.

However, in alternative embodiments, the use of guide systems is preferably minimized. As shown in FIG. 9, guide system 112A, 112B includes a series of contact points. Given the possible high tack level of the elastomeric fiber or thread, contact points are likely to undesirably add tension to the thread before reaching drive and tension control apparatus 110. As can be appreciated by those having ordinary skill in the art, it is generally preferable to stretch the thread with drive and tension control apparatus 110 before tension is added to the thread since tension added to the thread before the thread reaches drive and tension control apparatus 110 gets amplified by the drive and tension control apparatus 110.

The following paragraphs give exemplary details of the operation of the drive and tension control apparatus in terms of guide rolls 113A-113E, tension sensor 115, motion sensor 116, and break sensor 117. It is understood that these same details of operation are also applicable to guide rolls 113A′-113A′″ to 113E′-113E′″, tension sensors 115′-115′″, motion sensors 116′-116′″, and break sensors 117′-117′″.

According to a preferred embodiment, as shown in FIG. 9, guide systems 112A, 112B include a combination of static guides 128 and captive rolling guides 129. In addition, FIG. 9 shows guide rolls 113A-113E of the drive and tension control apparatus 110 direct the thread through the feeding system 103. Alternatively, any of the guide rolls 113A-113E may be eliminated from the drive and tension control apparatus 110 if an application performance can be improved through the use of fewer guide rolls.

The guide system 112A, 112B is typically attached to a central frame member 125. According to a particularly preferred embodiment, as the thread comes off the packages 105-108, 105′-108′, the thread is directed by static guides 128. If multiple threads are being used, multiple static guides 128 may be provided for each thread. Static guide 128 is preferably an orifice through which the thread passes. According to a preferred embodiment, the static guides 128 are substantially circular orifices. However, static guides 128 are not limited to having a circular orifice for directing the thread. As can be appreciated, alternative embodiments may use any known or appropriate guide device for directing the thread.

After the thread passes through the static guides 128 and the captive rolling guides 129, the thread engages a guide roll 113A-113A′″ configured to direct the thread to the drive and tension control apparatus 110. Again, if multiple threads are being used, a first guide roll 113A may be provided for each thread. Further, as most clearly shown in FIG. 13, if the thread feeding system 103 is supplying multiple thread groups to the thread processing system, multiple drive and tension control apparatus 110 and corresponding first guide roll 113A may be added. FIG. 10 shows first guide rolls 113A, 113A′, 113A″, 113A′″ are free-spinning idler rolls. According to a preferred embodiment, if a thread group having more than one thread is being directed to the drive and tension control apparatus 110, the first guide rolls 113A′, 113A″, 113A′″ for each thread spins independently of the other first guide roll 113A.

The tension controller device 119, as best shown in FIG. 10, is preferably a programmable device that implements a tension trimming algorithm in accordance to programs and parameters entered into the device. A non-limiting example of such a tension controller device is manufactured by Best Technologies Study and Research (BSTR), 21057 Olglate Olona, ITALY. In an alternative embodiment, the tension controller can be provided by Dover Flexo Electronics, Inc., 217 Pickering Road, Rochester. The tension controller 119 may include, but is not limited to, a digital display or readout 121 that provides information on the controller operation and measurements, input means 123 such as buttons, keyboard, or a touch panel for inputting information, and indicator lights 125, such as light-emitting diodes, that represent the status of the device and alarms.

Multiple tension sensors 115, 115′, 115″, 115′″ may be used to determine a net tension value for a group of threads. Multiple break sensors 117, 117′, 117″, 117′″ determine whether there is a break in any individual thread or fiber. In addition, multiple motion sensors 116, 116′, 116″, 116′″ may be added to determine whether the individual thread or fibers are moving. Non-limiting examples of tension, breakage and motion sensors are also available from BTSR.

FIG. 10 is a top plan view of the four threads drive and tension control device shown in FIG. 9. FIG. 10 shows the motor 127 for the driven take-off roll 111 and the connection between the motor 127 and the tension controller device 119. Cable 120 is used to make the electrical connection for the control signals transmitted between the tension controller device 119 and the variable speed motor 127. A variety of electrical interfaces including but not limited to, serial bus, parallel bus, PMCIA bus and USB bus interfaces may be transmitted using cable 120. Signals from the tension controller device 119 are used to increment, maintain or decrement the speed of the variable speed motor 127. FIG. 11 is a right side elevational view of the tensioning trim module shown in FIG. 9 and FIG. 10.

As shown in FIG. 10, thread feeding system 103 includes a drive and tension control apparatus 110 that is used to increment, maintain or decrease the amount of tension in the elastomeric thread. The drive and tension control apparatus 110 includes a variable-speed motor 127 having a drive shaft attached to a driven take-off roll (FIG. 9, 111). Each thread of a thread group is wrapped around the same driven take-off roll (FIG. 9, 111). The surface of the driven take-off roll 111 may be relatively smooth, or in alternative embodiments, the surface may include one or more grooves extending substantially parallel to the thread path to further guide the thread 102, 102′, 102″, 102′″ while on the driven take-off roll 111.

The motor 127 shown in FIG. 9 and FIG. 10 is a variable speed motor. This is in contrast to the constant speed motors typically used in background art unwinding devices/thread feeding systems. The thread is wrapped around driven take-off roll 111 at an angle sufficient to minimize slippage and low enough to avoid tangling. The angle at which the thread is wrapped around driven take-off roll 111 is referred to as a “first wrap angle.” Preferably the first wrap angle (θ₁) is approximately between 2 degrees and 360 degrees. The first wrap angle (θ₁) may vary depending on the type of elastomeric thread of fiber being used and the corresponding level of tack. According to a particularly preferred embodiment, the thread is wrapped around driven take-off roll 111 at the first wrap angle (θ₁) of approximately 270 degrees.

As shown most clearly in FIG. 9, a second guide roll 113B engages the thread after coming off driven take-off roll 111 and cooperates with first guide roll 113A to define the first wrap angle (θ₁) of the thread around driven take-off roll 111. First guide roll 113A and second guide roll 113B may be selectively positioned to achieve the desired first wrap angle (θ₁).

As shown in FIG. 9, the drive and tension control apparatus 110 further includes a tension controller device 119 that is provided after driven take-off roll 111 to monitor the tension of the thread coming off driven take-off roll 111 and to alter the speed of motor 127 to control the tension of the thread 102, 102′, 102″, 102′″. The tension controller 119 is connected to a tension sensor 115. The tension sensor 115 determines a measure of the tension of the thread as the thread comes off driven-take-off roll 111 and generates a signal representative of that tension.

As shown in FIG. 9, the tension sensor 115 is positioned after driven take-off roll 111 and in the thread path. The distance the thread travels between the driven take-off roll 111 and tension sensor 115 is preferably minimized. Reducing the distance the thread travels between driven take-off roll 111 and tension sensor 115 enables the drive and tension control apparatus 110 to better account for tension variations occurring at the point where the correction is being made (i.e., at the driven take-off roll 111). A substantial distance between driven take-off roll 111 and tension sensor 115 may add additional tension variations not seen at the driven take-off roll 111.

As shown in FIG. 10, tension controller device 119 that is operably coupled to both tension sensor 115 and the variable speed motor 127. The tension controller device 119 is capable of recognizing the signal generated by tension sensor 115 indicating a variation in thread tension, and providing an output signal for maintaining the current speed, increasing the current speed, or decreasing current speed of motor 127 in response to such recognition. This output signal is communicated to the motor via interface cable 120, as shown in FIG. 10. The interface between the motor 127 and sensor may use any standard electronic interfaces. Examples of such standard electronic interfaces include, but are not limited to, serial bus, parallel bus, PCIbus, PMCIA and USBbus.

According to a preferred embodiment, tension sensor 115 is a strain gauge type sensor that provides an output voltage signal to tension controller device 119 that is representative of thread tension. According to a particularly preferred embodiment, a MagPower CL 1-5 tension sensor 115, from Magnetic Power Systems, Inc., 1626 Manufacturers Drive, Fenton, Mo., may be used. Alternatively a BTSR TS4 Series or a Dover Flexo Electronics, Inc. Model LT may also be used. As can be appreciated, the present invention may include any sensor suitable to provide an output signal representative of thread tension. As yet another alternative a load cell type sensor may also be used.

Guide rolls 113C, 113D and tension sensor 115 define a second wrap angle (θ₂) in the range of 0 to 180 degrees of circumference for the thread around the tension sensor 115. Preferably, the thread is wrapped over the range of 45 degrees to 180 degrees. Directing the thread through tension sensor 115 at the second wrap angle (θ₂) enables the tension sensor 115 to more easily be calibrated based on the type of thread and the number of threads being used. A predetermined second wrap angle (θ₂), at a predetermined tension, will provide a resultant force on the tension sensor 115 in the vertical direction. This resultant force is detected by tension sensor 115 and converted into an output signal that can be recognized by tension controller device 119.

According to a preferred embodiment, tension sensor 115 is calibrated to have a tension detection range between 0 grams and 500 grams. According to an alternative embodiment, tension sensor 115 is calibrated to have a range of detection between 0 grams and 1000 grams. As can be appreciated, tension sensor 115 may be calibrated to have a variety of ranges of tension detection depending on the application. In addition, alternative embodiments may utilize additional tension sensors variously located throughout the thread feeding system. However, as can be appreciated, these tension sensors may include a variety of characteristics and calibrations.

In addition, the tension sensor 115 supplies an output signal in the form of a voltage to then tension controller device 119 that is dependent on the thread tension. According to a preferred embodiment, tension sensor 115 provides an output voltage signal ranging from 0 volts to 10 volts that is representative of thread tension. However, as can be appreciated, in alternative embodiments, these tension sensors may utilize a variety of voltage, current, magnetic or other representative signals and a variety of ranges for these representative signals.

According a particularly preferred embodiment, the variable speed motor 127 is a servomotor and the tension controller device 119 is a servo driver having a built in PID controller. One vendor providing such controllers is Emerson Control Techniques, 12005 Technology Drive, Eden Prairie, Minn. 55344. A non-limiting example of such a variable speed motor is the Emerson Control Techniques Unimotor Series, Model 75EZB301CACAA, which may use a Emerson Control Techniques Undrive Series, Model SP1201, Drive Controller. This variable speed motor drive system includes an internal tension PID so that an external PLC or other motor controller is not required. The system has an approximate update time of 250 microsecond (μs) on the tension input. Another example of such a system is the BTSR Model SMDIN/RW Controller and KTF/100RW Feeder Motor. Variable-speed motor drive systems are well known, as are the corresponding control systems. Accordingly, further details of their operation will not be provided here. However, it should be understood that the thread speed in the present invention may be driven and controlled by any suitable or otherwise appropriate drive and control system.

The thread feeding system 103, as shown in FIG. 6 to FIG. 11, provides for net tension control of a thread group being supplied to an application of the thread processing system. In addition, thread feeding system 103 may provide for a separate net tension control of a second thread group being supplied to a second application of the thread processing system. As used herein, net tension refers to the resultant tension of the group of threads passing over the same driven take-off roll 111. By controlling the net tension of a first thread group, and separately controlling the net tension of a second thread group, tension variations for each thread group may be corrected where background art unwinding devices/thread feeding systems typically could not make such a correction.

FIG. 12 is an exemplary enlarged front elevational view of a single thread drive and tension control apparatus 110. The drive and tension control apparatus 110 comprising a driven take-off or driven take-off roll 111, guide rolls 113A-113E, a tension sensor 115, breakage sensors 117, motor 127 and a tension controller device 119. Optionally, a motion sensor (not shown) may also be included. The tension controller device 119 further comprises a graphical display, a keyboard, and alarm lights.

FIG. 13 is a front elevational view showing two drive and tension control apparatus 110, each having four feed roll packages 105-108, 125-128 mounted vertically on a support frame 109. FIG. 14 is an exemplary perspective view showing another support frame configuration 109 for a thread feeding system 103 that supports a set of active packages 105, 106 and standby packages 105′, 106′. FIG. 15 is a top plan view of the thread feeding system 103 shown in FIG. 14.

The concept of net tension control for a thread group may be further explained using the diaper manufacturing as thread processing system example. According to a preferred embodiment, as shown in FIG. 13, thread feeding system 103 includes two thread groups 104, 104′ having two threads per group. Each thread group is driven by a separate drive and tension control apparatus 110 with a separate driven take-off roll 111. Both thread groups may be supplied to a diaper manufacturing process to provide the elastic band features near the open end of the legs. A first thread group may provide the elastic feature for the right leg portion, and a second thread group may provide the elastic feature for the left leg portion. During manufacturing, the tension of the elastic feature for the right or left leg portion may no longer be at an acceptable level due to tension variations in the thread. Thread feeding system 103 enables the tension of the first thread group or the second thread group to be adjusted independently of the other thread group in order to correct any such variations.

In operation, a thread processing system is likely to provide a signal to the tension controller 119 of the drive and tension control apparatus 110 indicating what speed motor 127 should operate at to provide the necessary elongation to achieve a desired tension. The signal from the thread processing system is typically based on industry standards that have been created indicating the theoretical amount of elongation necessary to achieve a desired tension. This input signal from the thread processing system is referred to as the tension set point and initially dictates the speed of the driven take-off roll 111 of the drive and tension control apparatus 110.

According to a preferred embodiment, a user enters a desired tension range that is to be maintained for the thread group directly into tension controller device 119. The tension controller device receives input signals from the tension sensor 115 representative of the thread tension. Tension controller device 119 uses these input signals to determine whether the tension level of the thread coming off driven take-off roll 111 can be maintained because it is within the desired tension range, or whether the tension needs to be increased or decreased. Variable-speed motor 127 of the drive and tension control apparatus 110 will maintain a speed until tension controller device 119 outputs a signal indicating that the net tension is outside the desired range based on a signal received from the tension sensor 115. The output signal from tension sensor 115 will override an input signal from the thread processing system and change the speed of the variable speed motor 127 of the drive and tension control apparatus 110 until the speed is within the desired range. That is, the speed of motor 127 will be adjusted to correct for variations in tension that occur during unwinding or the thread feeding process.

If the tension controller device 119 determines that the thread tension after driven take-off roll 111 is too high, the tension controller device 119 will increase the speed of motor 127. Alternatively, if the tension controller device 119 determines that the thread tension after driven take-off roll 111 is too low, the tension controller device 119 will decrease the speed of motor 127.

As described above, thread feeding system 103 may be configured to look at a signal from the thread processing system as well as a signal from the tension sensor 115 in determining the appropriate speed for motor 127. In alternative embodiments, the drive and tension control apparatus 110 of thread feeding system 103 may be configured to look only at a signal from tension sensor 115 (i.e., a tension feedback signal) in determining the appropriate speed for motor 127. Further, thread feeding system 103 may include multiple sensors positioned throughout the system that determine the appropriate speed of motor 127.

According to another alternative embodiment, as shown in FIG. 16, thread feeding system 203 may be configured with separate drive and tension control apparatus 210 to control the tension of each thread separately. Controlling the tension of each thread separately may advantageously be used to correct variations in each active package. Junction boxes 219A and 219C contain cabling and power connections to the tension control apparatus 210. Junction box 219B contains, for example, the BTSR Model SMDIN/RW Controller, as the tension controller device 219 for each drive and tension control apparatus 210. Controlling the thread tension for each thread separately is in contrast to the apparatus shown in FIG. 9 and FIG. 10, where the thread feeding system 103 controlled the net thread tension of a thread group. Controlling the net thread tension of a thread group tension corrects overall variability in the combined packages, but does not separately correct for variability for individual active packages in the thread group.

As shown in FIG. 17, drive and tension control apparatus 210 includes a separate variable-speed motor 227 and a corresponding separate tension sensor 215 for each individual thread. While such a system may advantageously correct variations in each active package, use of such a system may not be cost efficient considering the costs of motors, tension sensors, and tension controller devices.

According to a preferred embodiment, the speed of motor 227 is controlled without receiving input from a thread processing system. That is, the motor speed is based solely on tension feedback detected by tension sensor 215 and recognized by tension controller device 219.

When only a single thread is being driven by driven take-off roll 211, the guide system for a thread feeding system may be simplified as compared to a system using multiple threads wherein thread paths must be kept separate. For example, thread feeding system 203, as shown in FIG. 16, may use a guide system 212 having only a static guide 212A, such as a ceramic eye, through which the thread passes after coming off package 205, and a first guide roller 213A to direct the thread towards driven take-off roll 211.

In the single thread configuration shown in FIG. 16, the control of the speed of motor 227 is based solely on tension feedback. In this case, the changes in speed are likely to occur more frequently and in larger increments/decrements than a thread feeding system controlled by a tension set point provided by a thread processing system in combination with tension feedback, as discussed above. In particular, a large decrement in the speed of motor 127 may cause slack in the thread before reaching driven take-off roll 211 which may lead to a subsequent slippage of the thread around driven take-off roll 211.

To reduce the likelihood of such slack in the thread before reaching driven take-off roll 211, a pretensioner may be used in the first guide roll 213A. Background art pretensioners rely on friction between the thread and the pretensioner to maintain tension in the thread feeding system and avoid slack in the thread. However, such friction-type pretensioners are not applicable to elastomeric threads where tack is an issue. Accordingly, pretensioner guide roll 213A uses a pretensioner which otherwise hinders the speed of rotation of the guide roll. In a preferred embodiment for pretensioner guide roll 213A, a magnet is positioned adjacent to pretensioner guide roll 213A and a material that is coupled to the guide roll. The material to be coupled to the guide roll is, for example, a ferrous metal such as steel. The magnetic force slows the rotational speed of the pretensioner guide roll 213A and thereby maintains the tension and eliminates slack in the thread without relying on friction.

As shown in FIG. 17, after the thread is directed around pretensioner guide roll 213A, the thread is wrapped around driven take-off roll 211. A tension sensor 215 is positioned after driven take-off roll 211. The guide roll 213B is located after driven take-off roll 211. In addition, the tension sensor 215 may also be simplified because only a single thread is being used.

FIG. 18 is an exemplary enlarged front elevational view of a second embodiment of a single threads drive and tension control apparatus 210. As shown in FIG. 18, after the thread is directed around pretensioner guide roll 213A, the thread is wrapped around driven take-off roll 211. In particular, the thread is wrapped around driven take-off roll 211 at an angle sufficient to minimize slippage and low enough to avoid tangling. The angle at which the thread is wrapped around driven take-off roll 211 is referred to as a “first wrap angle.” Preferably the first wrap angle (θ₁) is approximately between 2 degrees and 360 degrees. The first wrap angle (θ₁) may vary depending on the type of elastomeric thread of fiber being used and the corresponding level of tack. According to a particularly preferred embodiment, the thread is wrapped around driven take-off roll 211 at the first wrap angle (θ₁) of approximately 270 degrees. The first wrap angle (θ₁) can be obtained by the proper positioning of guide rolls 213A, driven take-off roll 211, and tension sensor 215.

The tension sensor 215 is positioned after driven take-off roll 211. The guide roll 213B is located after driven take-off roll 211. The thread maintains a second wrap angle (θ₂) across tension sensor 215 that provides an accurate and consistent measurement of the thread tension in the range of 0 to 180 degrees of circumference. The thread is pressed against the thread guides before and after the tension sensor to guarantee a consistent second wrap angle (θ₂). The second wrap angle (θ₂) can be obtained by the proper positioning of guide rolls 213B, driven take-off roll 211, and tension sensor 215. A tension controller device 219 monitors the thread tension measured by tension sensor 215 and at least one of increments, maintains or decrements the speed of the variable-speed motor 227.

FIG. 19 is a right side elevational view of the drive and tension control apparatus 210 shown in FIG. 18. As shown in FIG. 19, after the thread is directed around the driven take-off roll 211 which is driven by motor 227, the thread passes through the tension sensor 215 and out of the apparatus via guide roll 213B.

FIG. 20 is a top plan view of the single threads drive and tension control apparatus shown in FIG. 18. As shown in FIG. 20, after the thread is directed around pretensioner guide roll 213A, the thread is wrapped around driven take-off roll 211. A tension sensor 215 is positioned after driven take-off roll 211. The guide roll 213B is located after driven take-off roll 211

FIG. 21 an exemplary enlarged front elevational view of a third embodiment of a single thread drive and tension control apparatus 210. As shown in FIG. 21, after the thread is directed around pretensioner guide roll 313A, the thread is wrapped around driven take-off roll 311 which is driven by motor 327. In particular, the thread is wrapped around driven take-off roll 311 at an angle sufficient to minimize slippage and low enough to avoid tangling. The angle at which the thread is wrapped around driven take-off roll 311 is referred to as a “first wrap angle.” Preferably the first wrap angle (θ₁) is approximately between 2 degrees and 360 degrees. The first wrap angle (θ₁) may vary depending on the type of elastomeric thread of fiber being used and the corresponding level of tack. According to a particularly preferred embodiment, the thread is wrapped around driven take-off roll 311 at the first wrap angle (θ₁) of approximately 270 degrees. The first wrap angle (θ₁) can be obtained by the proper positioning of guide rolls 313A, driven take-off roll 311, and tension sensor 315.

A tension sensor 315 is positioned after driven take-off roll 311. The guide roll 313B is located after driven take-off roll 311. The thread maintains a second wrap angle (θ₂) across tension sensor 315 that provides an accurate and consistent measurement of the thread tension in the range of 0 to 180 degrees of circumference. The thread is pressed against the thread guides before and after the tension sensor to guarantee a consistent second wrap angle (θ₂). The second wrap angle (θ₂) can be obtained by the proper positioning of guide roll 313B, driven take-off roll 311 and tension sensor 315. A tension controller device 319 monitors the thread tension measured by tension sensor 315 and at least one of increments, maintains or decrements the speed of the variable-speed motor 327.

FIG. 22 is a top plan view of the third embodiment of the single threads drive and tension control apparatus 310 shown in FIG. 21. As shown in FIG. 21, after the thread is directed around pretensioner guide roll 313A, the thread is wrapped around driven take-off roll 311. A tension sensor 315 is positioned after driven take-off roll 311. The guide roll 313B is located after driven take-off roll 311. A tension controller device 319 monitors the thread tension measured by tension sensor 315 and at least one of increments, maintains or decrements the speed of the variable-speed motor 327.

FIG. 23 shows a flow diagram for the tension trim algorithm 2301 of the method of monitoring threads or fiber tension of the present invention. In step 2303 of FIG. 23, the method determines whether any of the threads or fibers is broken. When a broken thread or fiber is detected, a BREAK ALARM is set in step 2305 and the tension trim algorithm 2301 is stopped at step 2327A.

When no broken threads or fibers are detected in step 2303, the method determines whether the threads or fibers are moving in step 2304 of FIG. 23. When the threads or fibers are not moving, a MOTION ALARM is set in step 2309 and the tension trim algorithm 2301 is stopped at step 2327B. When the threads or fibers are moving, a measurement of the tension of the moving threads or fibers occurs in step 2311.

In step 2312 of FIG. 23, the method determines whether any of the individual thread or fibers has a tension that is outside of a predetermined range. The predetermined range is preferably defined by at least one of the mean range tension and maximum tension as disclosed in TABLE 1 to TABLE 5 above. Alternatively, any acceptable predetermined range of tensions may be used with the thread feed processing system. When an out-of-range value of tension is detected, a TENSION ALARM is set in step 2313.

In accordance with whether the out-of-range tension is above or below the predetermined range, the motor speed is decremented or incremented, respectively, in step 2314. The number of increments and decrements in the motor speed over the course of the algorithm are stored in step 2320. When an individual thread or fiber tension has a value that is out-of-range, the method determines whether the number of increment/decrement steps that is stored in step 2320 exceeds a correction threshold in step 2318.

When no out-of-range tension values are detected for the individual threads or fibers, the method determines an average value for the tension of multiple threads or fibers in step 2315 of FIG. 23. In addition, the average value for the threads or fiber tension is stored in step 2317.

In step 2318 of FIG. 23, the method determines whether the average value for the threads or fiber tension is outside of a predetermined range. The predetermined range is preferably defined by at least one of the mean range tension and maximum tension as disclosed in TABLE 1 to TABLE 5 above. When an average value for the thread or fiber tension has a value that is out-of-range, the method determines whether the number of increment decrement steps, previously stored in step 2320, exceeds a correction threshold in step 2323.

The correction threshold is a predetermined value that is entered in the trim tension algorithm 2301 at initialization and may be updated in real-time. The predetermined value is a maximum number of corrections that are to be allowed by the algorithm before operator intervention is suggested. The values for the predetermined value of the correction threshold may be different in terms of the number of decrements and the number of increments that are determined to exceed the threshold.

When the correction threshold has been exceeded, by either or both the number of increments or decrements, a TENSION UPDATE alarm is set in step 2325 and the tension trim algorithm 2301 is stopped at step 2327C. When the tension trim algorithm 2301 is stopped at either of steps 2327A, 2327B or 2327C, as discussed above, the operator can read the alarm status of the equipment and take the appropriate steps to intervene and correct the process.

When the average value of the thread or fiber tension is not out-of-range, the method maintains the motor speed, as indicated in step 2321 and returns to step 2303 to repeat the above discussed trim tension monitoring algorithm.

The foregoing description of the present invention provides illustration and description, but is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The scope of the invention is defined by the claims and their equivalents.

The foregoing figures (FIG.) show particular unwinder systems used to feed elastomeric threads to a thread processing system. However, it should be understood that the present invention is not limited to the configuration of the unwinder systems shown. Alternative unwinder systems also fall within the scope of the present invention even if they vary from the unwinder systems shown in a variety of ways not limited to but at least including: (1) number of threads being fed; (2) types of packages supported; (3) positioning and use of guide members; and (4) number and type of drive systems. In particular, the present invention is suitable for use with any unwinder system where it would be desirable to monitor and control the tension of elastomeric or other types of thread in order to minimize tension variations in the thread from being introduced into a thread processing system.

In addition, though the figures illustrate a particular unwinder system that uses the OETO method for unwinding a package, it should be understood that the present invention is equally suitable for use with unwinder systems that do not use the OETO method. In particular, the present invention applies to all unwinder systems where a tension monitoring and tension adjusting system can be used to enhance efficiency and/or quality of thread processing systems using elastomeric or other types of threads.

Further, the written description of the preferred and other exemplary embodiments discusses the applicability of the present invention for providing elastomeric thread to a thread processing system in the form of a diaper manufacturing system. In particular, the application is preferably directed at the task of supplying elastomeric thread to be used for the elastic band features present near the open end of the legs of the diaper. While the present invention is shown in a diaper manufacturing environment, such illustration is not intended to be limiting and is included for exemplary purposes only. It will be understood by those skilled in the art after reading the description that the present invention is equally suitable for use for any other manufacturing process that utilizes an elastomeric thread.

Further, though only a few exemplary embodiments of the present invention have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible in these embodiments (e.g., types of rack systems, guide systems, drive systems, and control systems; sizes, structures, shapes and proportions of the various elements and mounting arrangements; and use of materials in terms of combinations and shapes) without materially departing from the novel teachings and advantages of the present invention.

Furthermore, the order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating configuration and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the inventions as expressed herein. 

1. A thread feeding system comprising: a support frame; a fiber package holder affixed to said support frame for holding a package of thread about a rotational axis such that at least one thread can unwind from the package in a direction defining an acute angle with the rotational axis of the package; a driven take-off roll for unwinding thread from the package at a predetermined take-off rate: a first static guide for directing fiber unwound from the fiber package, said first static guide positioned on said frame such that; a distance (d) from the first static guide to the end of the package facing the first static guide, measured on the line defined by the rotational axis of the package, is equal to: at least about 0.41 meter for thread with tack of greater than about 2 grams OETO and less than about 7.5 grams OETO; or from about 0.71 meter to about 0.91 meter for fiber with tack greater than about 7.5; an angle (θ), defined by the intersection of imaginary lines corresponding, respectively, to the rotational axis of the package and the central axis of the first static guide inlet orifice that is equal to: 0° to about 30° for threads with tack greater than about 2 grams OETO and less than about 7.5 grams OETO; or 0° to about 10° for threads with tack levels greater than about 7.5 grams OETO; and a drive and tension control apparatus for sensing and controlling the speed of the driven take-off roll, wherein the drive and tension control apparatus controls the speed of a variable-speed motor for the driven take-off roll by determining whether at least one of the mean tension and maximum tension is within a predetermined range of thread tension values.
 2. The thread feeding system of claim 1, wherein the thread is an elastomeric thread.
 3. The thread feeding system of claim 1, wherein a first wrap angle of the thread around the driven take-off roll is in the range between 2 and 360 degrees.
 4. The thread feeding system of claim 1, wherein a first wrap angle of the thread around the driven take-off roll is approximately 270 degrees.
 5. The thread feeding system of claim 1, wherein the drive and tension control apparatus further comprises guide rolls and a tension sensor, and wherein a second wrap angle of the thread around the tension sensor is in the range between 0 and 180 degrees.
 6. The thread feeding system of claim 5, wherein a guide roll that precedes the driven take-off roll is a pretensioner guide roll.
 7. The thread feeding system of claim 6, wherein the pretensioner guide roll creates pretension from the thread by using a magnet positioned adjacent to the pretensioner guide roll and a ferrous material coupled to the guide roll.
 8. The thread feeding system of claim 7, wherein the ferrous material is at least one of metal and steel.
 9. A drive and tension control apparatus comprising: guide rolls configured to guide at least one thread through a thread path of the drive and tension control apparatus; a driven take-off roll configured to move the at least one thread through the drive and tension control apparatus; a variable-speed motor configured to drive the driven take-off roll; a tension sensor configured to determine the tension on the at least one thread; a tension controller device configured to at least one of increment, maintain and decrement a speed of the variable-speed motor, wherein the guide rolls are located before and after the driven take-off roll, the tension sensor is located after the driven take-off roll, and wherein the speed of the variable-speed motor is maintained within a predetermined range of thread tension values by the tension controller device.
 10. The drive and tension control apparatus of claim 9, wherein the thread is an elastomeric thread.
 11. The drive and tension control apparatus of claim 9, wherein a first wrap angle of the thread around the driven take-off roll is in the range between 2 and 360 degrees.
 12. The drive and tension control apparatus of claim 9, wherein a first wrap angle of the thread around the driven take-off roll is approximately 270 degrees.
 13. The drive and tension control apparatus of claim 9, wherein the drive and tension control apparatus further comprises guide rolls and a tension sensor, and wherein a second wrap angle of the thread around the tension sensor is in the range between 0 and 180 degrees.
 14. The drive and tension control apparatus of claim 13, wherein a guide roll that precedes the driven take-off roll is a pretensioner guide roll.
 15. The drive and tension control apparatus of claim 14, wherein the pretensioner guide roll creates pretension from the thread by using a magnet positioned adjacent to the pretensioner guide roll and a ferrous material coupled to the guide roll.
 16. The drive and tension control apparatus of claim 15, wherein the ferrous material is at least one of metal and steel.
 17. A method for controlling thread tension in a thread feeding system, comprising: determining whether threads are broken; determining whether threads are moving; measuring the tension of the moving threads; determining whether any of the moving threads have a tension that is out-of-range relative to predetermined tension values; at least one of incrementing and decrementing the speed of a driven take-off roll when the tension is out of range and at least one of the number of increments and decrements is below a correction threshold; determining whether an average tension for the moving threads is out-of-range relative to the predetermined tension values for the threads; at least one of incrementing and decrementing the speed of a driven take-off roll when the tension is out of range and at least one of the number of increments and decrements is below a correction threshold; and setting an alarm when the threads are at least one of broken, not moving and out-of-range and above a correction threshold, wherein the value that determines that the tension is out-of-range are in accordance with predetermined tension values for the threads. 